Effect of capping and particle size on Raman laser-induced degradation of γ-Fe2O3 nanoparticles

Spectroscopy studies of NiFe2O4 nanosized powders obtained using coconut water

“…Although most of the Raman peaks for NiFe 2 O 4 ferrite (Fig. 3) are close to ␥-Fe 2 O 3 , the ␥-Fe 2 O 3 exhibits much stronger peaks at 1370 cm −1 and 1580 cm −1 than the NiFe 2 O 4 ferrite [5,30]. In this range, very weak Raman absorption peaks are observed (Fig.…”

“…To avoid measurement errors the same quantity of finely powdered samples has been packed in calibrated capillary quartz tubes. The g factor (spectroscopic splitting factor) was calculated from the formula h = gˇH [30], where h is the Planck's constant, the frequency,ˇthe Bohr magneton and H the external magnetic field (at half of the peak-to-peak of the first derivative spectra). The amplitude of the EPR signal (A) was assumed to be proportional to the product of peak-to-peak derivative intensity (Ipp) and the square of peak-to-peak width ( Hpp) 2 (Eq.…”

“…In the preparation of NiFe 2 O 4 ferrite, the formation of small amount of impurity such as Fe 3 O 4 , ␣-Fe 2 O 3 and ␥-Fe 2 O 3 is often observed and Raman spectroscopy has been used to differentiate NiFe 2 O 4 from other possible phases, such as Fe 3 O 4 and ␥-Fe 2 O 3 , which have similar spinel structures and consequent similar XRD patterns [5,13,30]. Although most of the Raman peaks for NiFe 2 O 4 ferrite (Fig.…”

New evidences of in situ laser irradiation effects on γ‐Fe2O3 nanoparticles: a Raman spectroscopic study

“…[1,2,3] Although a considerable amount of work has been devoted to γ -Fe 2 O 3 nanoparticles, the mechanism of laserinduced phase transition for nanoparticle sizes below 10 nm has not yet been investigated, to the best of our knowledge. However, some difficulties were reported in the literature for the preparation and the stabilization [4,5] or degradation [6] of metastable pure γ -Fe 2 O 3 crystallites during heating treatment. It has been concluded that the transformation of metastable γ -Fe 2 O 3 phase into the more stable hematite phase (α-Fe 2 O 3 ) within the temperature range 300-600 • C is highly dependent on the crystallinity and the particle size, i.e.…”

Atomic layer deposition of ferromagnetic iron oxide films on three-dimensional substrates with tin oxide nanoparticles

“…g-Fe 2 O 3 can be seen as an iron deficient form of magnetite [21]. Like all spinel ferrites, g-Fe 2 O 3 is ferromagnetic, but the presence of cation vacancies in the octahedral site likely does not allow a spin arrangement exactly similar to Fe 3 O 4 and, possibly, the antiferromagnetic spin arrangement in this ferrite enables antiparallel close spin sites similar to a-Fe 2 O 3 and this may give rise to the observed band at 1320 cm -1 [22].…”